The present invention relates to a fuel cell system and, more particularly, an auto-thermal reformer fuel cell system to produce electricity.
Fuel cell power plants for producing electricity are well known in the art. U.S. Pat. No. 3,976,507 discloses a pressurized fuel cell power plant which operates at a pressure greater than ambient pressure. While the power plant disclosed in U.S. Pat. No. 3,976,507 is effective and useful for generating electricity, the fact that the plant operates under pressure does not render it particularly useable for an auto-thermal reformer fuel cell system with vehicular applications. In a low pressure auto-thermal reformer fuel cell system, the size of the system and the pressure drop experienced during operation of the system are critical factors in producing an effective, compact system which is useable in vehicular applications.
Naturally, it would be highly desirable to produce an auto-thermal reformer fuel cell system which can operate effectively at ambient pressure while maintaining a compact size which is suitable for use in the system. In order to achieve the foregoing, each component in the auto-thermal reformer fuel cell system must be designed in a manner which takes into consideration the allowable pressure drop which may occur within the system and the sized limitation constraints necessary to make such a system practical. Therefore, any savings in size and pressure drop which can be obtained with any of the system components is highly desirable. Accordingly, it is a principal object of the present invention to provide a compact precooler which is useful in an auto-thermal reformer fuel cell system.
It is a particular object of the present invention to provide a compact precooler which is effective in reducing the temperature of a reformer exit gas stream while ensuring minimal pressure drop.
It is a still further object of the present invention to provide a compact precooler between an auto-thermal reformer and low temperature shift converter which provides sufficient residence time to effectively cool the reformer exit gas stream to a desired temperature and evaporate all water used in the precooler.
It is a still further object of the present invention to provide a process for cooling a reformer exit gas stream in an effective manner while limiting pressure drop.
Further objects and advantages of the present invention will appear hereinbelow.
The foregoing objects and advantages are obtained by way of the present invention by providing, in a near ambient pressure operated auto-thermal reformer fuel gas system, a precooler between the auto-thermal reformer and low temperature shift converter. The precooler includes an atomizing water inlet which also includes an inlet for the reformed gas wherein the inlet for reformed gas comprises a plurality of jets arrayed circularly about the atomizing water inlet and at an acute angle with respect to the longitudinal axis of the precooler so as to create a swirling and recirculating flow of the reformed gas in the cooler thereby increasing the residence time so as to effectively cool the hot reformed gas.
It is noted, however, that other types of fuel processing devices such as thermal steam reformers or partial oxidation devices could benefit from the use of a compact precooler in fuel cell systems incorproating such devices.
The present invention is further drawn to a process for cooling a reformed exit gas from an auto-thermal reformer operated at near ambient pressure so as to ensure a cooled reformed gas at the desired temperature wherein the gas stream is substantially free of water droplets. By vaporizing all the water in the precooler, the process ensures a minimal pressure drop from the inlet of the precooler to the outlet of the precooler.